West Nile Encephalitis and West Nile Virus Prevention

The most effective way to reduce the risk of contracting West Nile virus is to avoid contact with mosquitoes during the months of April to October. Mosquitoes are active in the early morning, from dawn until 10 a.m., and in the later afternoon and early evening. Limit outdoor activities or take the following precautions:

If outside during dawn and evening hours, when mosquitoes are most active, wear protective clothing such as long-sleeved shirts, long pants, and socks.

Use an insect repellent containing 10%-30% DEET solution. Children should not use a DEET repellent stronger than 10% strength. Other precautions when using DEET include avoiding use on infants or pregnant women, avoiding prolonged or excessive use, storing DEET out of the reach of children, and preventing children from applying it themselves. Adults should apply DEET products to children following manufacturer's instructions.

Spray clothing with repellents containing permethrin or DEET because mosquitoes may try to bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. If clothing is sprayed, there is no need to spray repellent containing DEET on the skin under the clothing. For details on pesticide application, check the National Pesticide Information Center.

Citronella, frequently used in outdoor candles, is a good deterrent against mosquitoes; however, it does not provide long-term protection.

Limiting mosquito habitats and breeding grounds may also help limit human exposure. Mosquitoes lay their eggs in standing water, so dispose of all tin cans, plastic containers, rubber tires, or any other possible water-holding containers from nearby property. Mosquito larvacides may be used. Drain water from pool covers. Make sure roof gutters drain properly and clean gutters regularly.

Make sure doors and windows have tightly fitted screens without holes.

Birds who have died from West Nile virus pose no health risk. The disease is only transmitted by a mosquito bite. Mosquitoes become infected by biting birds that harbor the virus. Report dead birds (especially crows and blue jays) to local health officials so they can be tested and the virus tracked. Touching dead birds is not recommended; if a dead bird must be removed or handled, wear gloves.

Development of a vaccine: Since the virus first appeared in New York, researchers began looking for a vaccine. There are several vaccines available for horses, but these vaccines are not approved for use in humans. Research is ongoing; currently, there is no vaccine available for humans against WNE.